Method for exchanging data between a plurality of subscribers by means of a data bus

ABSTRACT

The invention relates to a method for exchanging data between a plurality of subscribers (K 1 , K 2 , K 3 , K) by means of a data bus. The subscribers are located in their totality in at least two spatially and physically separate subordinate data buses and exchange, in the interval in which the more rapid data bus is not busy, data via control devices that are associated with every subordinate data bus and that are interconnected via a more rapid data bus.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of German patent document 100 26245.7, filed 26 May 2000 (PCT International Application PCT/EP01/05434,filed 12 May 2001), the disclosure of which is expressly incorporated byreference herein.

This application is related to co-pending U.S. patent application Ser.No. 10/296,343, filed Jul. 24, 2003.

The invention relates to a method and a network for exchanging databetween a plurality of subscribers via a data bus.

Modern vehicles frequently include several (preferably standardized)data buses. For engine and chassis components, for example, one systemis used which is adapted to that application, while another suitablydesigned bus system is used for audio and telecommunication peripheries.Data exchange between the different bus systems takes place by way of aplurality of gateways.

An attempt to transfer this bus system architecture which is used inhigher-priced vehicles to vehicles of the lower cost, however, resultsin high expenditures, due on the one hand, to the high costs of thestandard bus for engine and chassis components and, on the other hand,to the cost of a gateway. The construction of a separate onboard networkstructure for lower priced vehicles is problematic in that it is largelyimpossible to take over individual components of the higher-pricedvehicles because of a lack of compatibility. In addition, a conflictarises due to differing goals. To lower the cost, the transmission ratecan be reduced and the number of bus subscribers can be increased, whichresults in long response times and low flexibility, because subscribernumbers differ from one vehicle to the next. Every addition of a newsubscriber (for example, as a result of a subsequently installedcomponent) requires considerable adaptation expenditures.

It is an object of the invention to provide a highly efficient method ofexchanging data between several subscribers via a data bus which canserve a plurality of subscribers that vary in a vehicle-specific manner.

The onboard network structure according to the invention is modular andcost-effective. It permits the use of the same basic components in allvehicles covering several model series of a manufacturer. Thehigher-quality vehicles can be arbitrarily equipped with additionalcomponents, without being more expensive than comparable series systems.

A prerequisite for the invention is the existence of a faster data bus,such as for example the data bus described in German Patent Documents DE19636441 A and DE 19636442 A. This data bus is distinguished by atransmission rate of more than 5 Mbits/s and is suitable, for example,for passive safety systems, such as air bags, belt tighteners, and thelike, as well as the pertaining sensor system and actuators and theircontrol units.

The control units are situated at different points of the vehicle (forexample, in the area of the transmission tunnel or the B-columns, in thedoor or at the steering column). All such control units are connectedwith the data bus which, in normal situations (that is, outside a crashphase or serious misuse phase), is not utilized to a great degree. Thesame applies to the utilization of the processors in the control units.

According to the invention, these control units are also used for otherfunctions. These functions are part of a different function periphery,for example, the electronic system of the vehicle body, and relate, forexample, to the light control, the wiper control, the central lockingsystem and the window lift mechanism control.

The light control and the wiper control, on the one hand, and thecentral locking system and the window lift mechanism control, on theother hand, are each a component of a subordinate data bus. Because ofthe minimized number of subscribers (in the case of the light control,for example, one control unit and 10 connected subscribers), thesubordinate data bus has a sufficient response time and is also operableat a low transmission rate. That is, it rapidly and securely providesthe connected subscribers with the required data, or it to be provided.As a result it is possible to connect control units in the electronicsystem of the vehicle body (with higher demands on the communication)directly to the faster data bus.

With such an onboard network structure, the need for a separate data busfor the components of the electronic system of the vehicle body iseliminated, because these components are connected to the faster databus, either directly or via otherwise existing control units. Thisresults in the elimination of the gateway functionality, and thus ofseparate gateways.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE shows a data bus structure according to the inventionand an onboard network system of a vehicle implemented thereby, and thecommunication process implemented thereby is described.

DETAILED DESCRIPTION OF THE DRAWINGS

The block diagram illustrated in the FIGURE includes, among otherthings, a control unit module SGM and control units S1 to S4. In theirentirety, these components are part of a passive safety system and areconnected by a faster data bus “Sl bus” having a transmission rate of,for example, 5 Mbits/s. A plurality of control units “K” are connectedto the control units S1–S4, and separately form subordinate data busesK-bus cluster 1, K-bus cluster 2, K-bus cluster 3, . . . , which arecoupled respectively to the control units S1 to S4 as well as to thecontrol unit module SGM. The components SGM and S1 to S4 thereforecontain the functions of the passive safety system as well as the basicfunctions of the electronic system of the vehicle body. (Within thesubordinate data buses, several control units K are separately markedK1, K2 and K3 for the purpose of further explanation.)

With respect to the basic functions of the electronic system of thevehicle body, the control units SGM and S1 to S4 adapt the format of thedata of the subordinate data bus subscribers to the data format of thefaster data bus, or vice versa. They also control the feeding of datafrom the subordinate data bus subscribers to the faster data bus, andguide the data of the subscribers of the other subordinate data buses tothe subscribers of their connected subordinate data bus. For thispurpose, the data of all subscribers of both the subordinate data busand the faster data bus are provided with an unambiguous identification.The identifications of the subscribers of the connected subordinate databus are stored in the respective control unit.

One advantage of the data bus structure according to the invention isthat the number of messages per subordinate data bus is significantlylower than in the case of a data bus with only one branch. Moreover, asa result of the small number of subscribers, the waiting time to apossible bus access is short.

In order to provide a system which is as flexible as possible, it isnecessary that subordinate data bus subscribers (in the case of K-bussubscribers) basically have access to all required information of theoverall system. In addition, it should be possible without any basicchange to “clamp over” a K-bus subscriber from one subordinate data busto another. As a result, it is possible, for example, to place a windowlifter switch block in one vehicle series in the door and in the othervehicle series on the center console.

The K-bus addresses are unambiguous throughout the entire system. Thecorresponding K-bus messages are transposed according to a fixed rule,to bus messages of the faster data bus with corresponding IDs. In thecontrol units SGM and S1 to S4, encodable “mini-gateway tables” thencause the transposition of only messages which are needed in therespective subordinate data bus. Therefore, for the “transfer” of onecontrol unit K from one subordinate data bus to another, only thesegateway tables need then be recoded. The overall system behaviortherefore remains absolutely unchanged.

The data exchange within the overall system is explained by an example.For transmission of a K-bus message TK1 from subscriber K1 at the K-buscluster 1 to subscriber K2 at the K-bus cluster 2, K1 sends message TK1to K-bus cluster 1, triggered, for example, by a pressure on a key. SGMreceives TK1 and wraps the message TK1 into the data field of an Sl busmessage. Each Sl bus subscriber receives TK1 in the Sl bus format andchecks in its gateway table whether TK1 is to be transmitted to itspertaining K-bus cluster. S1 unwraps TK1 from the Sl bus format andtransmits TK1 to the K-bus cluster 2. K2 receives TK1.

If the messages of the K-bus subscribers have a longer length than thatof the data of the Sl bus (for example, 32 bytes of useful data incomparison to 12 bytes of useful data), a segmented (that is, repeated)transmission of defined telegram parts is required.

If, for any reason, not K2 but K3 is to receive the TK1, TK1 needs onlybe deleted from the gateway table of S1 and be entered into the gatewaytable of S2.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A method of exchanging data between a plurality of subscribers via adata bus, wherein: said subscribers are arranged in at least first andsecond spatially and physically separate subordinate data buses; controlunits are assigned to each subordinate data bus and are mutuallyconnected by way of a third data bus; said subscribers exchange data viasaid assigned control units and said third data bus, at times when thethird data bus is not busy; and the third data bus has a fastertransmission capacity than the first and second subordinate data buses.2. The method according to claim 1, wherein the control units adapt aformat of data of the subordinate data bus subscribers to a data formatof the faster data bus, or vice versa.
 3. The method according to claim1, wherein each of the subordinate data bus subscribers and subscribersof the faster data bus has an unambiguous identification.
 4. The methodaccording to claim 3, wherein an identification of each of thesubscribers of the connected subordinate data bus is stored in a controlunit to which it is coupled.
 5. The method according to claim 3, whereinthe identification of the subscribers of not connected subordinate databuses are stored in the respective control unit.
 6. The method accordingto claim 3, wherein the identification of the not connected subscribersare contained in a programmable memory.
 7. Method according to claim 6,wherein data transmission from the subordinate data bus to the fasterdata bus and vice-versa is controlled by means of memory content.
 8. Adata network structure for a vehicle, comprising: a primary data bushaving a first data transmission rate capacity; a plurality of controlunits connected via said primary data bus; a plurality of subordinatedata buses, each having a second data transmission rate capacity that issmaller than said first data transmission rate capacity and beingphysically and spatially separated from other subordinate data buses,one such subordinate data bus being connected to each respective controlunit; and a plurality of subscribers connected to each of saidsubordinate data buses, wherein said subscribers to said subordinatedata buses exchange data via said primary data bus and the control unitsto which said subscribers are coupled, during periods when said primarydata bus is not otherwise in use.
 9. The data network structure for avehicle according to claim 8, wherein: each of said subscribers has aunique identification code; and each of said control units has anencodable table containing information from transposition of onlymessages directed to the subordinate data bus connected thereto.
 10. Themethod according to claim 1, wherein said control units comprise atleast first and second control units, one such control unit beingconnected to each of said first and second subordinate data buses,respectively.
 11. A method of exchanging data among a plurality ofsubscribers via a data communication network, wherein: each of saidsubscribers is connected in data communication with one of at least twospatially and physically separate subordinate data buses which areincluded in said data communication network; said data communicationnetwork, further includes at least two control units which are connectedin data communication with each other via a primary data bus, one suchcontrol unit being connected to each of said subordinate data buses,respectively; said subscribers exchange data via said control units andsaid primary data bus at times when said primary data bus is not busy;and said primary data bus has a faster transmission capacity than thesubordinate data buses.